In an optical disk drive apparatus, it is common to generate a track error signal (TES) to indicate the positional deflection value of a spot of a laser beam from a track center. In track following operation mode wherein an optical head (beam) follows a track, the movement of the optical head is controlled so that the value of TES remains zero. However, a track following operation sometimes fails due to a disturbed TES caused by an external mechanical shock or vibration, etc. or a flaw or fault, etc. on an optical disk.
In a conventional method, a tracking servo is interrupted when the failure of track following operation is detected. In such a conventional method, it is impossible to recover a track following operation since the TES remains at a high frequency, as shown in FIG. 6. Further, in a conventional method, it is sometimes impossible to recover a track following operation, as shown in FIG. 7, since a TES cannot be obtained because the optical head is run into the mirror part of an optical disk during the interruption. Accordingly, in such a conventional method, the initial operation is required to restart after the optical head is stopped and a long time to recover the track following is required.
Japanese Published Unexamined Patent Application (PUPA) No. 63-179476 discloses an apparatus wherein upon switching a tracking servo from off to on, a velocity servo is firstly operated for a predetermined period of time in order to decrease the frequency of the TES before the tracking servo operation is started. This prior art does not relate to the recovery of the track following operation after interruption.